1. Field of the Invention
This invention relates to a latch mechanism used in a wafer container to provide sealed housing space for the transport or storage of a wafer container, and particularly to a latch mechanism for clamping the box of the wafer container tightly to the base plate of the wafer container for providing air-tight sealing.
2. Description of the Prior Art
During wafer fabricating processes, in order to prevent the wafer from contamination of particles in ambient atmosphere, the wafer is usually held in a completely sealed container.
U.S. Pat. No. 4,995,430 disclosed a sealable transportable container for such purpose. It includes a box sealable to a bottom wall by a latch mechanism located on the bottom wall. The latching is accomplished by means of a cam mechanism actuating a latch plate to move linearly so that a latch finger at one end thereof can engage with a latch engaging surface of the box. A riser is provided on the roller surface of the cam mechanism for providing pivoting motion of the latch plate so that the finger end of the latch plate can press the box tightly against the bottom wall when the cam mechanism is turned to a required position.
However in the event of no anti-counter rotation positioning means being provided, or the cam mechanism not being turned to the required position (e.g. being turned only to one half of the angle required), the vibration and impact forces resulting from handling or transportation of the box, and the compressing force applied on the latch plate caused by the riser can cause the cam mechanism to produce counter rotation and consequently resulting in the box being separately from the bottom wall. Furthermore, the cam mechanism disclosed in the U.S. Pat. No. 4,995,430 includes pivot post, pins, slots, cam lobes, slant camming surface, springs, etc. It is a complex structure composed of a lot of components. It is therefore expensive to produce.